Rat peritoneal PMNs are associated with the early proteins of the complement system but not C5b-9/MAC in vitro, shown by flow cytometry. Cells (5 × 106/ml) labeled with a FITC-conjugated anti-PMN antibody and a Cy5-conjugated antibody for C1q (B), C3 (C), or C5b-9 (D), or appropriate IgG controls (A) showed that nearly all cells were PMNs (B, C, & D), but only some cells were associated with C1q (B & E) and C3 (C & E); however, these cells were not associated with C5b-9/MAC (D & E). All flow cytometric gates were set using control IgG isotype labeled cells. # = significantly differ from IgG control. n = 3. Number of experiment replication = 3.